[SOLVED] modules_install fails in chroot

Question

I've been using Funtoo on my main desktop PC for quite some time. Now I'm expanding the family building a small (and "weak") NAS and I'd like to have the OS on a USB key, easy to move and clone.

I created a chroot environment on the desktop and installed Funtoo inside it; it all went well, except that when I tried to compile a new kernel ( gentoo-sources-4.15.4 ) the modules_install phase fails: more specifically, depmod.sh fails. As consequence, apparently, the kernel fails to boot.

I tried different methods: manual compilation, genkernel and genkernel-next, all with the same result.

It worth mentioning that the two CPU are different, but both x86_64 and I modified the *FLAGS accordingly.